The invention generally relates to a photographing apparatus and a photographing method, and in particular, to a photographing apparatus including an image pickup device having a plurality of pixels arranged in a matrix form and a photographing method thereof.
Japanese Patent Laid-Open Gazette No. H11-41523 discloses performing a front curtain of a shutter operation with an electronic shutter and performing a rear curtain of the shutter operation with a mechanical shutter in a photographing apparatus equipped with a Complementary Metal-Oxide Semiconductor (CMOS) type image pickup device.
In addition, Japanese Patent Laid-Open Gazette No. 2007-159061 (“the '061 patent”) and Japanese Patent Laid-Open Gazette No. 2007-53742 (“the '742 patent”) disclose the technology for preventing light-exposure stains from occurring due to a difference of a lens type, an iris value, or a shutter speed by changing a timing of starting charge accumulation in every area or line in a method of mixing an electronic shutter and a mechanical shutter.
The '061 and '742 patents aim at compensation for a conventional image quality problem generated by changing a mechanical front curtain to an electronic reset function. Thus, it is set that an operation timing of an electronic shutter for a front curtain has almost the same characteristics as an operation timing of a mechanical shutter for a rear curtain. In addition, for causes changing shutter characteristics, such as a lens type and an iris value, an operation timing is set by considering compensation parameters.
The electronic shutter performs a function as a front curtain of a shutter for starting light-exposure of an image pickup device by discharging charges accumulated in the image pickup device. A time required to fully discharge the charges accumulated in the image pickup device is commonly defined in a specification of each photographing apparatus by defining a valid pulse width of a charge discharging pulse. In a case of a number of lines in a vertical direction due to a number of pixels, it is necessary for a pulse width of the charge discharging pulse to be narrow in order to make a light-exposure start speed of the electronic shutter follow a traveling speed of the rear curtain of the mechanical shutter. However, if the pulse width of the charge discharging pulse becomes narrow, the charges accumulated in the image pickup device cannot be fully discharged, so remaining charges occur, thereby increasing an afterimage effect.